Large cabinet signs, which can also be referred to as box signs, typically use fluorescent bulbs and a ballast as the lighting system. As seen in FIG. 1, a sign housing 12 and translucent panels 14 define a hollow enclosure and fluorescent tubes 16 and a ballast (not shown) mount inside the enclosure. The fluorescent tubes 16 illuminate both the front panel and the rear panel, but fluorescent tube lighting has its drawbacks.
Fluorescent tubes emit light in a 360 degree pattern from a central axis. Light that is emitted from the top and bottom portions of the tube is generally wasted and does not reflect well toward the translucent panels. This decreases the efficiency of the system.
The typical life for the lighting system of box signs illuminated using fluorescent lamps is about 12,000 hours, which is measured as when fifty percent of the lamps have burned out. It would be desirable to increase the lifetime of the lighting system that is used to illuminate the box sign.
High intensity discharge (HID) lamp fixtures have also been used in large signs. The HID lamps typically include lenses that are placed over the individual fixtures to preferentially spread light across the backside of each panel. High intensity discharge lamps, however, are susceptible to unintended dimming at low temperatures. Similarly, fluorescent lamps lose efficiency and efficacy at lower temperatures.